Polyamides of trimethylhexamethylenediamine and cyclohexane dicarboxylic acid

ABSTRACT

Polyamide of a diamine of the group 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and mixture thereof, and dicarboxylic acid comprising cycloaliphatic dicarboxylic acid. The polyamides are soluble in alcohols so that they are suitable for use in formulation of film forming compositions.

Unite States Patent Schmitt et al. [45] Sept. 19, 1972 [54] POLYAMIDESOF TRIMETHYLHEX- 2,939,862 6/ 1960 Caldwell et al ..260/78AMETHYLENEDIAMINE AND 2,965,615 12/1960 Caldwell et al. ..260/ 78CYCLOHEXANE DKCARBOXYLIC 3,150,117 9/1964 Gabler ..260/78 ACIDInventors: Karl Schmitt, Heme; Fritz Gude, Wanne-Eickel; SiegfriedBrandt, l-lerne, all of Germany Assignee: Scholven-ChemieAktiengesellschaft,

Gelsenkirchen-Buer, Germany Filed: June 26, 1969 Appl. No.: 836,950

Foreign Application Priority Data July 2, 1968 Germany ..P 17 70,7663

0.8. Ci. ..260/78 R, 260/312 N, 260/33.4 R Int. Cl. ..C08g 20/20 Fieldof Search ..260/78 References Cited UNITED STATES PATENTS 12/1959Caldwell et al. ..260/78 FOREIGN PATENTS OR APPLICATIONS 619,576 3/1949Great Britain ..260/78 Primary Examiner-i-larold D. AndersonAttorney-Burgess, Dinklage & Sprung [5 7] ABSTRACT 3 Claims, No DrawingsPOLYAMIDES OF TRlMETHYLHEXAMETHYLENEDIAMINE AND CYCLOHEXANE DICARBOXYLICACID BACKGROUND It is known that transparent polyamides having very goodmechanical properties can be obtained by the condensation of2,4,4-trimethylhexamethylenediamine and/or2,2,4-trimethylhexa-methylenediamine with aromatic dicarboxylic acids,especially terephthalic acid.

These types of polyamide are not soluble in ordinary solvents and behavein this regard like the crystalline polyamides. This makes it impossibleto use them for many purposes, such as the manufacture of cast films,varnish films, etc.

THE INVENTION prepared, for example, which can be worked in the form ofa solution in higher alcohols but which are insoluble in ethanol andparticularly in mixtures of ethanol and water. Copolyamides of thisgroup, whose dicarboxylic acid content consists of to 50 percent1,4-cyclohexanedicarboxylic acid and 90 to 50 percent terephthalic acid,are characterized by an unusually high notch impact toughness.

Hexahydroterephthalic acid is an example of a dicarboxylic acid that canbe used with the diamines according to this invention. Ifbenzenedicarboxylic acids are used, terephthalic and/or isophthalicacid, for example can be used. The acid component can consist up to 90percent of terephthalic acid and/or isophthalic acid.

The condensation to polyamides according to this patent application isperformed under the usual conditions. For example, the dicarboxylic acidor derivative,

It has now beenfound that polyamides ha i hi h 'e.g. ester, and thediamine, with-or without the addition thermal stability, which aretransparent and have good solubility in alcohols, can be prepared bycondensing 2,4,4-trimethylhexamethylene diamine and/or 2,2,4-trimethylhexamethylenediamine with one or more cycloaliphaticdicarboxylic acids, mixed, if desired, with one or more aromaticdicarboxylic acids. This finding is surprising because for one thing thereplacement of aromatic components in polymers by cycloaliphatic, i.e.hydroaromatic components of otherwise the same structure, results in agreat reduction of thermal stability. On the other hand, the torsionmodulus curve of the polyamide prepared fromcyclohexane-l,4-dicarboxylic acid and trimethylhexamethylenediamine, forexample, is virtually identical to the curve of the polyamide preparedfrom terephthalic acid and trimethylhexamethylenediamine. The sameapplies to the softening points according to Vicat. Anothercycloaliphatic acid well suited for the purposes of the invention isl,3-cyclohexanedicarboxylic acid.

The starting product for the preparation of the diamine in question isisophorone,which is catalytically hydrogenated to3,5,S-trimethylcyclohexanbl and is then oxidized to form the isomermixture of l,-l,3- and l,3,3- trimethyladipic acid. To prepare an isomermixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, the isomerictrimethyladipic acids are converted to the corresponding dinitriles andthen the compound is hydrogenated.

If it is desired to obtain pure 2,4,4- or 2,2,4-trimethyl-hexamethylenediamine, the isomeric trimethyladipic acids areseparated by known methods and converted separately to the correspondingdiamines.

Solubility in alcoholic solvents makes it possible to make polyamidesprepared from cyclohexanedicarboxylic acids and trimethylhexamethylenediamine into highly filled molding compounds and into varnish films andcast films. The molding compounds are useful for production of shapedobjects, in the usual manner; the films are useful as protectivecoverings.

Copolyamides prepared from cyclohexandicarboxylic acids,benzenedicarboxylic acids and trimethylhexamethylenediamine, which arealso transparent, have also proven interesting. The incorporation ofbenzenedicarboxylic acids makes it possible to control the solubilityproperties, so that polyamides can be of water, or in the form of theirsalts or an aqueous solution of their salts which can easily be preparedby known methods, are heated slowly in a reactor to 200 to 300 C, and,after a precondensation period, the water formed by the condensation isconstantly removed. The water of condensation can additionally beremoved by the application of a vacuum. v

Instead 'of the freeacids, the diesters, semi-esters, acid chlorides oramides can be used according to known methods, i.e., in general thosecompounds which can react with diamines to yield a volatile compound andform polyamides, can be used. The molecular weights (numerical. average)are to be greater than 15,000 and preferably greater than 20,000 inorder to achieve the purposes of the invention.

The examples that follow shall serve to explain the present patentapplication. The trimethylhexamethylen'e diamine used in the examples isan isomeric mixture of the 2,2,4 and 2,4,4 isomers prepared as isdescribed above.

The reduced specific viscosity (Nred) determined at determined at 20 Cin a 1 percent solution in pure formic acid, shall serve as the measureof the molecular weight of the polyamides.

EXAMPLE 1 A mixture of 1,563 g of cyclohexane-l ,4-dicarboxylic acid,1,443 g of trimethylhexamethylenediamine and 2,000 ml of water is heatedunder nitrogen in a small pot equipped with an agitator, raising it fromto C within 5 hours, and from that to 260C within an additional 3 hours,2.3 liters of water being distilled off. After 2 hours at saidconditions, the mixture is stirred in a vacuum of 2 Torr at 260 C untilno more water is distilled of, and is then discharged under a nitrogenpressure of 30 atmospheres. The N red of the polyamide amounted to 0.75,corresponding to an average molecular weight of 2528,000.

The polyamide was dissolved in ethanol and applied to a steel plate.After air drying, during which the ethanol evaporated, a clearcontinuous film was obtained which showed no clouding after storage inwater and did not soften at temperatures under l40 C, and which was aprotective covering for the steel plate.

EXAMPLE 2 EXAMPLE 3 A mixture of 1,229 g og dimethylterephthalate, 422 gof l,4-cyclohexanedicarboxcylic acid dimethylester, 1,348 g oftrimethylhexamethylenediamine and 2,000 ml of water is boiled for 1 hourwith refluxing to saponify the ester. Then the water mixed with methanolis distilled off and the remainder is condensed by 3 to 4 hours ofheating at 260 c, appling a vacuum at the end. The polyamide can beworked on injection molding machines. The notch impact toughness ofspecimens runs around l5 to 20 kpcm/cm".

A 35 percent solution of the polyamide in an alcoholic mixture of 70percent by weight methanol, by weight water, percent by weight tolueneis applied to a steel plate. After the film had dried, a cupping of 8.9mm according to Erichsen (DIN 53l56) was formed, and a hardness of thefilm according to Buchholz (DIN 53153) of was measured.

EXAMPLE 4 A mixture of 600 g of l,3-cyclohexanedicarboxylic aciddimethyl ester, 988 g of isophthalic acid and 1415 g oftrimethyl-hexamethylenediamine and 2000 ml of water is boiled withrefluxing for l hour to saponify the esters. After the removal of waterand methanol by distillation, the remainder is condensed by 5 hours ofheating at 260 C. The polyamide can be worked both in ethanolic solutionform and by injection molding. The following values were measured:

Notch impact toughness: no breakage Ultimate bending stress: 1304 kg/cmBall pressure hardness: 1630 kg/cm Thermal stability of shape accordingto Martens: 1 10 C.

What is claimed is:

l. Polyamide consisting essentially of the polymeric condensationproduct of at least one of 2,4,4-trimethylhexamethylene diamine or2,2,4-trimethylhexamethylene diamine and at least one of 1,3- or 1,4-cyclohexane dicarboxylic acid, said polyamide having a numerical averagemolecular weight greater than 15,000 as determined by measuring thereduced viscosity of said polyamide in a 1 percent solution in pureformic acid at 20 C.

2. Polyamide according to claim 1 wherein the dicarboxylic acid isl,4-cyclohexanedicarboxylic acid.

3. Polyamide according to claim I wherein the dicarboxylic acid isl,3-cyclohexanedicarboxylic acid.

2. Polyamide according to claim 1 wherein the dicarboxylic acid is1,4-cyclohexanedicarboxylic acid.
 3. Polyamide according to claim 1wherein the dicarboxylic acid is 1,3-cyclohexanedicarboxylic acid.